To be or not to be possessive?
Interacting with many people expands students vision and broadens their horizons.
1. Plural noun + Noun
This is not possible. It is not grammatically correct.
2. Singular noun + Noun
- The first noun gives information about the second noun.
- student tells us what kind of vision
- The reference to the first noun is impersonal and abstract.
- Usually the first noun is inanimate (not a living thing or a group of living things):
- I can't find my pencil case.
3. Plural noun + possessive + Noun
- The first noun tells us who possesses the second noun.
- (the vision that is possessed by students)
- The reference to the first noun is personal and concrete.
- The first noun is nearly always animate (a living thing or group of living things):
- Men's magazines are displayed beyond the reach of children.
Returning to our opening example, meaning 3 would appear to be the most appropriate:
Interacting with many people expands students' vision and broadens their horizons.
This is partly because the second clause in the sentence - broadens their horizons - contains a possessive, and in order for the sentence to be parallel, both clauses need a possessive.